Go Down

Topic: First Project (Read 713 times) previous topic - next topic

huenemeca

Hello,
I am looking into buying parts for my first project and I have a few questions.

I am planning on using the Leonardo http://www.robotshop.com/productinfo.aspx?pc=RB-Ard-36&lang=en-US, will it work being run off of this charger and this battery?

http://www.robotshop.com/seeedstudio-usb-charger-power-booster-lipo-rider-pro.html
http://www.adafruit.com/products/258

The charger says it will step up the voltage to 5v but I just want to make sure.

Next question is that I want to run the motors off of a different battery. 

I am planning on using a simple small motor http://www.robotshop.com/tamiya-double-gearbox-70168.html unless you think that is too weak.
And a motor controller, http://www.robotshop.com/seeedstudio-grove-i2c-motor-driver-3.html

But I noticed that this motor controller says it needs 6 - 15 volts.  But my motor only needs 1.5 - 3.  So do I need a bigger battery? Or a different motor controller?

More questions to come but help with these will be great.

Thanks

liudr

I think those will work except for the seeedstudio motor control I'm not sure about. My guess is the voltage doesn't matter but please email the seller to confirm 3.7V will work.

Retroplayer

It looks like the motor shield has a voltage regulator on it, so it probably needs at least 6v for that reason more than the motors themselves. Putting too high of a voltage through your motor will cause too much current, shortening the life of the motor.

Though if you are using PWM to control the speed of the motor, the "average" voltage will be less than the total voltage, anyway. A 50% (127) duty cycle will halve the average voltage. So, you could just use the map() or constrain() functions to stay within PWM values that keep the average voltage below your motors voltage.

huenemeca

Ok, so the voltage regulator is to drive the I2C bus.  But I can power that using the connections from the Arduino.  So if I remove the jumper do you think it would work with lower voltage to passed to the motor?

Retroplayer

That jumper is to power the arduino from the 5V onboard regulator. Not the other way around. Removing the jumper would not power the arduino, but the board still requires a 6-15V power source in order to power it's own electronics. The on-board regulator powers all the logic on the board itself.

liudr


That jumper is to power the arduino from the 5V onboard regulator. Not the other way around. Removing the jumper would not power the arduino, but the board still requires a 6-15V power source in order to power it's own electronics. The on-board regulator powers all the logic on the board itself.


I am not all that sure about this. They don't even provide a schematic so there's no way to tell, between translation, that if the regulator can be circumvented by the jumper.

Retroplayer

Agreed, the more I read the datasheet the more confusing it is. However, what else is powering the electronics on the board if it isn't the 6 to 15V input through a regulator? This board is not a "shield"

huenemeca

Is there a better motor controller I should use?  This one seemed like the easiest for a beginner but now I am not sure.

If I do need a higher voltage battery I am having a hard time finding a charger for that larger lipo battery can you point me to one?

Thanks

liudr

Basic shield
https://shop.ruggedcircuits.com/index.php?main_page=product_info&cPath=4&products_id=38

Rugged shield
https://shop.ruggedcircuits.com/index.php?main_page=product_info&cPath=4&products_id=14

huenemeca

Both of those also say they are rated for 8 - 30 volts.  So I feel like I am back where I started.  I have a 3.7v battery so will this work?

liudr

My apologies. It turns out the L298 motor driver requires VIH+2.5 minimal for Vs, the voltage that drives the motor, where VIH is logic high, 5V in this case. So you have to supply 7.5V or up to the shield.

http://pdf1.alldatasheet.com/datasheet-pdf/view/22437/STMICROELECTRONICS/L298.html

huenemeca

Ok, thanks for the info.

Next quesiton.  If I wanted to get a more powerful motor.  That needs 6V.  I haven't seen many 7.2V lipo batteries.  But there are a few.  I see even less 7.2V lipo battery chargers.

I assume that I can't use the save charger for this bigger battery?  Can you point me to a charger and battery combo that would work?

liudr

I've not used a li-po battery or charger in my project  :smiley-roll-sweat:
I took a look again at that motor. It seems to be used for a dual wheel robot. In that case the motor only runs forward so a simple transistor will do. Does your design require the motors to turn backwards? I was searching low voltage motor drivers and found some but their packages need circuit boards.

huenemeca

Yeah, I am trying to build a simple RC car.  So I would like the wheels to run forward and backwards.  My next thought has been to use a bigger motor or 2 and get a bigger battery.  Then I can use this motor controller and would just need to find a good battery and charger.

I wanted to use a low voltage motor to make things simple, but I don't want it do be under powered.

Go Up